NEW CASTLE — The continued degradation of the Great Bay Estuary has prompted the creation of a new 10-year plan aimed at serving as a "blueprint" for preserving a marine habitat closely tied to the health of the entire Seacoast region.

Lawmakers, scientists and advocates supporting the Piscataqua Region Estuaries Partnership (PREP) gathered at Great Island Commons on Monday to officially launch an aggressive conservation plan that calls on all residents and municipalities to take action.

The "2010 Piscataqua Region Comprehensive Conservation and Management Plan" was officially signed during a ceremony that supporters hope signifies the beginning of a new era for a troubled estuary system.

PREP — a federally funded conservation partnership — has been working for years to draft and implement initiatives aimed at cleaning up Great Bay with the past 18-months having been used to draft a plan focused on addressing the latest pressing problems.

PREP Coastal Scientist Phil Trowbridge said among the major concerns are how increased development and nitrogen pollution is impacting a Great Bay Estuary that has been show to be in peril.

Trowbridge — a NH Department of Environmental Services employee — said nonpoint pollution sources like septic systems and fertilizers have introduced increasing amounts of nitrogen into the bay resulting in a threatening decline in eelgrass coverage on the bottom of the water body.

Studies showing a 37 percent decrease in eelgrass cover in Great Bay between 1990 and 2008 is threatening fish species and creating an environment were sediments can lift off the floor of the bay thus compromising water clarity.

"In general the estuary is in decline. We are at a juncture where we need to turn it around if we want these habitats to exist," Trowbridge said.

PREP has responded to the continued and emerging problems by putting together a new plan that will see individuals, state agencies, volunteers and municipalities from New Hampshire and Maine all working together to stem the tide of Great Bay's demise.

The strategy will look to initiate 86 different "action plans" that range from working with municipalities to eliminate the illegal discharges of sewers into surface waters to supporting continuing to monitor shellfish tissue samples to advocating for the removal of non-essential dams.

Officials said the plan directly impacts 52 New Hampshire and Maine towns on the estuary and will draw on 200 organizations in solving the problems.

PREP Director Rachel Rouillard made it clear that the plan is about brining together Seacoast residents of all walks of life so they might take part to address problems that were identified by "sound science."

U.S. Congresswoman Carol Shea-Porter praised the PREP a plan she called "ambitious."

"The degradation of our water resources is so serious we cannot waste any time," Shea-Porter said.

Representatives from numerous other NH and Maine congressional delegates also read letters supporting the plan.

Numerous individuals lauded the plan for what will be an unprecedented partnership that involved both New Hampshire and Maine working together on a major environmental project.

Assistant DES Commissioner Michael Walls pledged his agencies continued support on a preservation effort that he said is correctly looking at the estuary's threats from a holistic standpoint.

NH Fish and Game Executive Director Glenn Normandeau — a Portsmouth resident — said he didn't need to be convinced that the plan was important having grown up on the shores of what he called one of the state's most important "gems."

Normandeau said the plan will be worth nothing if individuals and organizations let it gather dust on the shelf so he urged action be taken to protect an estuary he noted "is easy to lose and impossible to replace."

He noted the habitats are caught between the "hammer and anvil" of climate change and population growth.

Major supporters of the new plan used Monday to sign a document showing their support with many noting the hardest work is yet to be done.

Individuals wanting to learn more about the 128-page plan can go to www.prep.unh.edu.